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Writer's pictureNik Foresteire, DO
Aug 53 min read

Tox Talk: Crotalid Envenomations

� How should the emergency department handle crotalid envenomations?


� What is a crotalid?

Defined as belonging to the Crotalidae (pit viper or viperidae) family, these snakes include rattlesnakes, copperheads, and water moccasins (cottonmouths). They are named due to heat-sensing pits between their eyes and nostrils.


� Native Viperidae Floridian Species & Where in Florida are they found?

  • Eastern Diamondback Rattlesnakes: Found universally across all regions.

  • Dusky Pygmy Rattlesnake: Found universally across all regions.

  • Florida Cottonmouth: Found universally across all regions.

  • Eastern Copperhead: A small portion of the northern panhandle

  • Canebreak "Timber" Rattlesnake: Northeastern Florida


� When are patients at most risk for envenomation?

Typical mating season occurs for most species between April to June with a gestational period of approximately 5 months. Most births occur from August to October. These two periods are typically when patients are at the highest risk of being bitten.


� Why does envenomation matter?

Envenomations account for over 10,000 annual emergency department (ED) visits in the United States. Presenting shortly after envenomation with an array of tissue, hematologic, or systemic effects, outcomes depend on ED physicians' timely intervention with one of the two available antivenoms.


� Indications for antivenom administration?

  • Necrosis

  • Swelling beyond a joint

  • Platelets < 150

  • PT > 15

  • Fibrinogen < 150

  • Systemic Effects (hemodynamic instability, angioedema, acute encephalopathy)


� What's in the bag??

  1. CRO-FAB (single fab)

  • What is it?

    • Crotalidae Polyvalent Immune Fab

    • Ovine (sheep)

  • Indications?

    • FDA Approved for Adults and Children

    • Use for: Rattlesnakes, copperheads and cottonmouths (water moccasins)

  • Contraindications?

    • Hypersensitivity to any known ingredients including papaya, papain, pineapple (bromelain)

  • Adverse Effects?

    • Recurrent coagulopathy requiring additional dosing up to 2 weeks

    • Serum sickness (fever, myalgias, arthralgias, etc.)

    • Anaphylaxis (angioedema, urticaria, pruritis) and severe allergic reaction

  • Dosing?

    • Initial dose: 4-6 vials IV over 1 hr, then observe for up to 1 hour

    • Repeat dose: 4-6 vial dose IV over 1 hour PRN

    • Additional: 2 vial dose IV over 1 hour, every 6 hours up to 18 hours (6 vials total)

  • Problems?

    • Each vial must be reconstituted with 18 mL of 0.9% Sodium Chloride and mixed

    • MUST BE PILL ROLLED SLOWLY with one to two inversions per second.

    • DO NOT SHAKE (if foaming occurs, it is essentially ruined)

    • The entire dose must be further diluted with 0.9% Sodium Chloride to a total volume of 250 mL

    • Must be stored in a refrigerator



2. ANAVIP (double fab)

  • What is it?

    • Crotalidae immune F(ab’)2

    • Equine (horse)

  • How does it work?

    • Venom-specific F(ab’)2 IgG fragments that bind and neutralize venom toxins, redistribute, and eliminate them from the body.

  • Indications?

    • FDA Approved for Adults and Children

    • Use for: All North American rattlesnakes, copperheads, and cottonmouths (water moccasins)

  • Contraindications?

    • None!

  • Special populations?

    • Pregnancy and lactating mothers

  • Adverse Effects?

    • Pruritus, nausea, rash, arthralgia, peripheral edema, myalgia, headache, pain in extremity, vomiting, and erythema

  • Dosing?

    • Initial: 10 vials IV over 60 minutes

    • Repeat: Up to 10 vials IV over 60 minutes as needed for control

    • Observation/Late Control: 4 vials IV over 60 minutes

  • Benefits?

    • 2 binding sites

    • Requires far less repeat dosing

    • Reconstitution in seconds, dose ready in minutes

    • Room temperature storage

    • Shelf life up to 3 years

  • Problems?

    • Most hospitals do not carry it.


➊ Study Performed?

  • The authors analyzed a database of 177 papers

    • Inclusion criteria:

      • Time: January 1970 to May 2020

      • Language: English

      • Keywords: "bite" and "crotalidae"

  • Criteria applied to answer 8 specific questions

  • 33 articles selected from 177


➋ Findings:

  • Initial evaluation and stabilize the patient (ABCDED tings)

  • Assess for local effects, hematologic effects, and systemic toxicity with suggestion of envenomation. Remember compartment syndrome (only if not responding to repeat dosing of antivenom)

  • Contact poison control EARLY (1-800-222-1222)

  • Toxic effects? Give Antivenom

  • Avoid surgery - aka fasciotomy and debridement

  • Antibiotics? Nope, not necessary


➌ Conclusions:

  • ED providers: Assess, stabilize, and intervene quickly

  • Antivenom?

    • Cro-Fab or ANAVIP, give whatever you have if signs of systemic toxicity

  • Stay Aways:

    • Tourniquets or any wound/surgical intervention

  • Antibiotics?

    • Not necessary

  • Wound?

    • Do not deroof any blistering

  • Disposition?

    • Medical admission

    • ICU for severe toxicity

  • Toxicology is awesome


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